Fact Check: The Draft and Offensive Line Play

One of the questions that has lingered regarding the Chicago Bears offensive line is whether or not Ryan Pace has “invested” enough high-level draft picks in the O-line. There is an argument made by fans and talking heads alike that a team needs multiple 1st-rounders on the offensive line in order to truly dominate the trenches.

I was curious about this idea, but I did not have the time to perform a truly deep dive across multiple years. Therefore, I simply posed a casual research question—was there enough evidence in place to suggest that this was a hypothesis worth testing in depth?

In order to determine that, I needed two points of comparison. First, I needed to know how I was going to evaluate offensive lines. I began with the % win rate for run blocking and pass blocking as reported by ESPN using NextGen Stats for 2020. I then cross-checked that with Pro Football Focus’s offensive line rankings for the same season. While I have little regard for PFF, a number of the people who think the draft position of the offensive line does matter seem to like their scoring system, so this seemed like a good cross-check.

The correlation between the composite rank for an offensive line’s win rates and Pro Football Focus’s rank was 0.65. That’s a notable correlation, albeit just barely. Overall, it was enough to convince me to run the numbers for both scoring systems (composite win rate and PFF), just to be thorough. Already, though, the process was suggesting why this is such easy fodder for armchair experts—with objective measures so dependent on other variables and subjective measures so vague, it is easy to claim that failures are because of poor investment in the offensive line without anyone being able to offer a strong rebuttal based on evidence.

Second, I needed to know which teams had what sort of investment in their offensive lines. Because this was intended to be a basic overview, I simply went through the starting rosters as reported by Pro Football Reference and checked the average draft position of the starters on each offensive line. I’ll admit that I was staggered by how diverse offensive lines really are, and I am definitely curious as to how the “survivor” number compare to the “total drafted” numbers. However, that is a project for another time.

Eighteen teams (56%) fielded 1st-round left tackles, sure. But 10 teams (31%) started left tackles drafted in the third round or later, and that includes five teams that were in the top ten when it comes to their composite win rate (50%). That actually means that left tackles taken after the first two rounds were disproportionately present on the better-performing offensive lines! For that matter, three teams in the top ten on PFF’s scoreboard (30%) also had left tackles drafted outside of the top two rounds, and that’s almost perfectly proportional. On first glance, it seems like it almost doesn’t matter if a team drafts a left tackle early or not. More on that later.

For now, offensive lines are incredibly diverse. Forty-six 1st-rounders were starters on the line, but so were forty-four players taken in the 6th-round or later (counting UDFAs). The other seventy starters were somewhere in between. When the relative success rates of 1st-rounders vs late-rounders is considered across the entire NFL, it speaks volumes when there are basically as many “lottery ticket” players starting as there are “blue chips”. True, there is a greater per-selection success rate for early picks. It probably takes many more attempts to find a starter in the sixth round than it does in the second round. However, it would almost take deliberate misrepresentation or obstinance to overlook the reality that teams consistently find starters in the later rounds or even after the draft is over.

The real question though, is whether or not these players are any good. With this much diversity across the line, the teams that skimped on talent in the trenches should be easily separated from the teams that invested heavily. It’s one thing to start a marginal player, but the teams that commit such folly must surely suffer for it, right?

Except they aren’t that different in results.

The correlation between win-rate rank and net offensive line draft position is 0.07, which is the next best thing to totally random and unconnected. The correlation between PFF rank and net offensive line draft position is 0.08, which isn’t really any better. Using composite totals for draft investment instead of relative ranks I was able to get the numbers to 0.09, but again this is basically random.

As a token gesture toward thoroughness, I tried isolating one position and one outcome. The average pass-blocking win rate of the teams with a 1st-round left tackle was 57%, good for an average rank of 17th . The average pass-blocking win rate for the other teams was 58%, with an average rank of 15th.

The conclusion is simple. While there is real variation up and down the lines regarding draft position, and while there is real variation up and down the offensive line in terms of performance, those two are not closely related. Heavy investment in the offensive line (relative to other teams) does not reliably show up in the actual performance of the offensive line. The 2020 Falcons had only 1st-round draft picks on their offensive line, but they had only the 24th-best composite win rate and the 21st-best performance rank per PFF. Meanwhile, five teams had at least two UDFAs on the line, with the Kansas City Chiefs (a 1st-rounder, a pair of 7th-rounders, and a pair of UDFAs) having the lowest total investment. They were 19th-best composite win rate and 11th-best rank per PFF.

I know that there are people who will point to an individual team’s performance and say “well they struggled because they didn’t invest in the line,” but depending on the threshold for investment, that could be said about any team except the Atlanta Falcons.

The lines with the greatest representation of high draft picks were (in order) the Falcons, the Saints, the Colts, the Vikings, and the Texans. All of them have at least four players taken in the first two rounds, and they only had an average rank of 13th in terms of win rate and 17th in terms of PFF rank. That’s pretty average, if a little better on win rate. Remove the Texans, and those four teams only have players taken in the fourth round or earlier, and all have multiple first-round selections playing. They have an average of the 14th-best win rate and the 16th-highest PFF rank.

On the other end of the spectrum, the Rams, Bills, Packers, Titans, and Jaguars all fielded lines without a single 1st-round starter. Of those lines, all but the Jaguars started at least two players who were undrafted free agents or taken after the third round. The first four teams on that list also averaged the 9th-best win rate and the 5th-best PFF rank.

Put simply, only one of the top five offensive lines in terms of composite win rate had a 1st-round left tackle, and only two of them started multiple 1st-rounders. Only one of the top five offensive lines per PFF had multiple 1st-rounders, and there were only four 1st-rounders across all twenty positions in the five best groups identified by PFF.

What’s the explanation for this? Is it possible that it doesn’t matter where a team finds an offensive lineman? Unlikely, but it’s not out of the question. Instead, what is more likely is that teams churn through late-round prospects readily on their offensive lines, and they are willing to cut the weak players and hang on to the stronger ones. As a result, by the time most teams determine their starters, they have very diverse groups. It is equally possible that while having highly drafted players matters, other factors (like continuity) matter even more.

None of this means that on a per-player basis a first-rounder is no more likely to work out than a fourth-rounder. Almost regardless of position, players taken earlier tend to do a bit better. However, it does mean that there is not any real sign that a team needs to invest elite picks in the offensive line in order to get elite play. It also means that people probably shouldn’t worry quite so much about the nuances between a high second-rounder (like Teven Jenkins) and a late first-rounder.